REPORT OF THE MALARIA EXI'EUITION. 
21 
male and female. They also drink water frequenth', and can often be seen to be distended with 
the fluid. Raw meat was offered to them, but the\- could not be observed to touch it. Earth 
placed at the bottom (jt the cage seems to be sin'table for them. 
According to the accounts of tlie soldiers at Wilberforce, the\' bite almo^t entireh' in the 
evening and m'ght, but liave beeti known to feed on men during the da\ . 'l'he\ can certaiiih be 
ted on men artificialh' during the da\ time, simph' b\' placing them in test-tubes and then appl\ ing 
the mouth of the tube to the skin. The stomach can be observed to become tlistended in from 
one to two minutes or more ; after which the insect continues to buck, but commences to 
evacuate b\' the anus serum containing a small percentage of red corpuscles. Culex voids only a 
clear fluid under tiie same circumstances. The insects sometimes continue sucking like leeches 
for five or ten minutes, voiding blood all the while ; but at other times soon withdraw the 
proboscis and then try another spot. It was noted, however, that Anoplu/rs fed in this maimer, 
even after they had remained sucking for Hve or ten minutes, never showed an\' great distension 
of the abdomen ; while the contents of the stomach still remained for some time transparent and 
red as seen through the scales of the living insect. Moreover, in these cases the meal was 
generally digested or voided within about 24 hours. 
On the other liand. Anopheles which had fed themseh es under natLU'al conditions generalh' 
presented a very different appearance. 'riie\' were enormoush' distended ; while the content^> ot 
the stomach were thick, opaque, and black, and sometimes did not disappear for three da\ s. 'J"he 
onl\- inference is that, under natural conditions, the insects which can manage to do so gorge 
tliemselves over and over again during the night - probably from the same subject. 
(3.) Propagation.- also observed that while naturalh -fed gnats invarial>l\^ laid eggs 
after two or three days, those which had been bred from the larvit in captivity, and had then been 
isolated and fed in test-tubes, nrvn did so, although before being isolated they had long been in 
company with males. The inference is that fertilization takes place onl\' after the female has 
been fed. 
We noted also that, in a cage where man\' male and female gJiats, both di/rx and 
Anopheles, were kept together tor weeks, eggs were never laid although the insects were ted as 
described on bananas, and the cage contained water for them to lay their eggs in. It seems, tlien, 
that a meal of blood is necessary before fertilization. 
Lastl)', we observed that previousU' fed and fertilized insects would la\' a second batch of 
eggs after a second meal of blood, without a second fertilization ; but never laid a second batch of 
eggs without a second meal of blood. That is, one fertilization suffices for several batches of eggs, 
but one meal of blood for only one batch of eggs. 
These observations are whoU)' in accord with the results of the prolonged study of many 
kinds of gnats made in India b\' one of us ; and it therefore seems likeh' that the followiiiij; law is 
likely to hold good for the CulicuLe which feed on men at least for the commoner species : 
Although these gnats can live indefim'tel)' on fruit and perhaps juices of plants, t)ie female 
requires a meal of blood, both for fertilization and for the development of her ova. In other words, 
the insects need blood for the propagation of their species. 
